---
id: events
title: Temporal Events reference
sidebar_label: Events
description: Events in a Temporal Service respond to external occurrences and Workflow Commands. Workflow Execution Event History includes WorkflowExecutionStarted, WorkflowExecutionCompleted, WorkflowExecutionFailed, and many more.
toc_max_heading_level: 4
keywords:
  - reference
tags:
  - Reference
---

[Events](/workflows#event) are created by the [Temporal Service](/clusters) in response to external occurrences and [Commands](/workflows#command) generated by a [Workflow Execution](/workflows#workflow-execution).
All possible Events that could appear in a Workflow Execution [Event History](/workflows#event-history) are listed below.

### WorkflowExecutionStarted

This is always the first [Event](/workflows#event) in a Workflow Execution Event History.
It indicates that the Temporal Service received a request to spawn the Workflow Execution.

| Field                              | Description                                                                                                                                                               |
| ---------------------------------- | ------------------------------------------------------------------------------------------------------------------------------------------------------------------------- |
| workflow_type                      | The [Name](/workflows#workflow-type) of [Workflow](/workflows) that was initiated.                                                                                        |
| parent_workflow_namespace          | The [Namespace](/namespaces) of the Parent [Workflow Execution](/workflows#workflow-execution), if applicable.                                                            |
| parent_workflow_execution          | Identifies the parent Workflow and the execution run.                                                                                                                     |
| parent_initiated_event_id          | Id of the [StartWorkflowExecutionInitiated](#startchildworkflowexecutioninitiated) Event this Event corresponds to.                                                       |
| task_queue                         | The [Task Queue](/workers#task-queue) that this [Workflow Task](/workers#workflow-task) was enqueued in.                                                                  |
| input                              | Information that is deserialized by the SDK to provide arguments to the Workflow.                                                                                         |
| workflow_execution_timeout         | The total timeout period for a [Workflow Execution](/workflows#workflow-execution), including retries and continue-as-new.                                                |
| workflow_run_timeout               | Timeout of a single Workflow run.                                                                                                                                         |
| workflow_task_timeout              | Timeout of a single Workflow Task.                                                                                                                                        |
| continued_execution_run_id         | [Run Id](/workflows#run-id) of the previous Workflow which continued-as-new, retried or was executed by Cron into this Workflow.                                          |
| initiator                          | Allows the Workflow to continue as a new Workflow Execution.                                                                                                              |
| continued_failure                  | Serialized result of a failure.                                                                                                                                           |
| last_completion_result             | Information from the previously completed [Task](/workers#task), if applicable.                                                                                           |
| original_execution_run_id          | The [Run Id](/workflows#run-id) of the original Workflow started.                                                                                                         |
| identity                           | The Id of the [Client](/self-hosted-guide/security#client-connections) or parent Workflow [Worker](/workers#worker) that requested the start of this Workflow.            |
| first_execution_run_id             | The first [Run Id](/workflows#run-id), along the chain of [Continue-As-New](/workflows#continue-as-new) Runs and Reset.                                                   |
| retry_policy                       | The amount of retries as determined by the service's dynamic configuration. Retries will happen until 'schedule_to_close_timeout' is reached.                             |
| attempt                            | The number of attempts that have been made to complete this Task.                                                                                                         |
| workflow_execution_expiration_time | The absolute time at which the Workflow Execution will [time out](/encyclopedia/detecting-workflow-failures#workflow-execution-timeout).                                  |
| cron_schedule                      | Displays the Workflow's [Cron Schedule](/workflows#temporal-cron-job), if applicable.                                                                                     |
| first_workflow_task_backoff        | Contains the amount of time between when this iteration of the Workflow was scheduled, and when it should run next. Applies to Cron Scheduling.                           |
| memo                               | Non-indexed information to show in the Workflow.                                                                                                                          |
| search_attributes                  | Provides data for setting up a Workflow's [Search Attributes](/visibility#search-attribute).                                                                              |
| prev_auto_reset_points             |                                                                                                                                                                           |
| header                             | Information passed by the sender of the [Signal](/encyclopedia/workflow-message-passing#sending-signals) that is copied into the [Workflow Task](/workers#workflow-task). |

### WorkflowExecutionCompleted

This indicates that the [Workflow Execution](/workflows#workflow-execution) has successfully completed. The [Event](/workflows#event) contains Workflow Execution results.

| Field                            | Description                                                                                                                           |
| -------------------------------- | ------------------------------------------------------------------------------------------------------------------------------------- |
| result                           | Serialized result of completed [Workflow](/workflows).                                                                                |
| workflow_task_completed_event_id | The Id of the [WorkflowTaskCompleted](#workflowtaskcompleted) that the Event was reported with.                                       |
| new_execution_run_id             | The [Run Id](/workflows#run-id) of the new Workflow Execution started as a result of a [Cron Schedule](/workflows#temporal-cron-job). |

### WorkflowExecutionFailed

This [Event](/workflows#event) indicates that the [Workflow Execution](/workflows#workflow-execution) has unsuccessfully completed and contains the Workflow Execution error.

| Field                            | Description                                                                                                              |
| -------------------------------- | ------------------------------------------------------------------------------------------------------------------------ |
| failure                          | Serialized result of a [Workflow](/workflows) failure.                                                                   |
| retry_state                      | The reason provided for whether the [Task](/workers#task) should or shouldn't be retried.                                |
| workflow_task_completed_event_id | The [Run Id](/workflows#run-id) of the [WorkflowTaskCompleted](#workflowtaskcompleted) that the Event was reported with. |
| new_execution_run_id             | The [Run Id](/workflows#run-id) of the new Workflow started by Cron or [Retry](/encyclopedia/retry-policies).            |

### WorkflowExecutionTimedOut

This [Event](/workflows#event) type indicates that the [Workflow Execution](/workflows#workflow-execution) has timed out by the [Temporal Server](/clusters#temporal-server) due to the [Workflow](/workflows) having not been completed within [timeout](/encyclopedia/detecting-workflow-failures#workflow-execution-timeout) settings.

| Field                | Description                                                                                                   |
| -------------------- | ------------------------------------------------------------------------------------------------------------- |
| retry_state          | The reason provided for whether the [Task](/workers#task) should or shouldn't be retried.                     |
| new_execution_run_id | The [Run Id](/workflows#run-id) of the new Workflow started by Cron or [Retry](/encyclopedia/retry-policies). |

### WorkflowExecutionCancelRequested

This [Event](/workflows#event) type indicates that a request has been made to cancel the [Workflow Execution](/workflows#workflow-execution).

| Field                       | Description                                                                                                           |
| --------------------------- | --------------------------------------------------------------------------------------------------------------------- |
| cause                       | The user-provided reason for the cancelation request.                                                                 |
| external_initiated_event_id | The [Run Id](/workflows#run-id) of the Event in the [Workflow](/workflows) that requested cancelation, if applicable. |
| external_workflow_execution | Identifies the external Workflow and the run of the its execution.                                                    |
| identity                    | Id of the [Worker](/workers#worker) that requested cancelation.                                                       |

### WorkflowExecutionCanceled

This [Event](/workflows#event) type indicates that the client has confirmed the cancelation request and the [Workflow Execution](/workflows#workflow-execution) has been canceled.

| Field                            | Description                                                                                     |
| -------------------------------- | ----------------------------------------------------------------------------------------------- |
| workflow_task_completed_event_id | The Id of the [WorkflowTaskCompleted](#workflowtaskcompleted) that the Event was reported with. |
| details                          | Additional information reported by the [Workflow](/workflows) upon cancelation.                 |

### WorkflowExecutionSignaled

This [Event](/workflows#event) type indicates the [Workflow](/workflows) has received a [Signal](/encyclopedia/workflow-message-passing#sending-signals) Event.
The Event type contains the Signal name and a Signal payload.

| Field       | Description                                                                                                     |
| ----------- | --------------------------------------------------------------------------------------------------------------- |
| signal_name | The name/type of Signal to be fired.                                                                            |
| input       | Information that is deserialized by the SDK to provide arguments to the Workflow function.                      |
| identity    | Identifies the [Worker](/workers#worker) that signaled to the Workflow.                                         |
| header      | Information passed by the sender of the Signal that is copied into the [Workflow Task](/workers#workflow-task). |

### WorkflowExecutionTerminated

This [Event](/workflows#event) type indicates that the [Workflow Execution](/workflows#workflow-execution) has been forcefully terminated and that likely the terminate Workflow API was called.

| Field    | Description                                                          |
| -------- | -------------------------------------------------------------------- |
| reason   | Information provided by the user or client for Workflow termination. |
| details  | Additional information reported by the Workflow upon termination.    |
| identity | Identifies the Worker that requested termination.                    |

### WorkflowExecutionContinuedAsNew

This [Event](/workflows#event) type indicates that the Workflow has successfully completed, and a new Workflow has been started within the same transaction.
This Event type contains last [Workflow Execution](/workflows#workflow-execution) results as well as new Workflow Execution inputs.

| Field                            | Description                                                                                                   |
| -------------------------------- | ------------------------------------------------------------------------------------------------------------- |
| new_execution_run_id             | The [Run Id](/workflows#run-id) of the new Workflow started by this Continue-As-New Event.                    |
| workflow_type                    | The name/type of Workflow that was started by this Event.                                                     |
| task_queue                       | The [Task Queue](/workers#task-queue) that this [Workflow Task](/workers#workflow-task) was enqueued in.      |
| input                            | Information that is deserialized by the SDK to provide arguments to the Workflow.                             |
| workflow_run_timeout             | Timeout of a single Workflow run.                                                                             |
| workflow_task_timeout            | Timeout of a single Workflow Task.                                                                            |
| workflow_task_completed_event_id | The Id of the [WorkflowTaskCompleted](#workflowtaskcompleted) that the Event command was reported with.       |
| backoff_start_interval           | The amount of time to delay the beginning of the [ContinuedAsNew](#workflowexecutioncontinuedasnew) Workflow. |
| initiator                        | Allows the Workflow to continue as a new execution.                                                           |
| last_completion_result           | Information passed by the previously completed Task to the ongoing execution.                                 |
| header                           | Information passed by the sender of the Signal that is copied into the Workflow Task.                         |
| memo                             | Non-indexed information to show in the Workflow.                                                              |
| search_attributes                | Provides data for setting up a Workflow's [Search Attributes](/visibility#search-attribute).                  |

### WorkflowTaskScheduled

This [Event](/workflows#event) type indicates that the [Workflow Task](/workers#workflow-task) has been scheduled.
The SDK client should now be able to process any new history events.

| Field                  | Description                                                                                |
| ---------------------- | ------------------------------------------------------------------------------------------ |
| task_queue             | The [Task Queue](/workers#task-queue) that this Workflow Task was enqueued in.             |
| start_to_close_timeout | The time that the [Worker](/workers#worker) takes to process this Task once it's received. |
| attempt                | The number of attempts that have been made to complete this Task.                          |

### WorkflowTaskStarted

This [Event](/workflows#event) type indicates that the [Workflow Task](/workers#workflow-task) has started.
The SDK client has picked up the Workflow Task and is processing new history events.

| Field              | Description                                                                                                 |
| ------------------ | ----------------------------------------------------------------------------------------------------------- |
| scheduled_event_id | The Id of the [WorkflowTaskScheduled](#workflowtaskscheduled) Event that this Workflow Task corresponds to. |
| identity           | Identifies the [Worker](/workers#worker) that started this Task.                                            |
| request_id         | Identifies the Workflow Task request.                                                                       |

### WorkflowTaskCompleted

This [Event](/workflows#event) type indicates that the [Workflow Task](/workers#workflow-task) completed.

| Field              | Description                                                                                                 |
| ------------------ | ----------------------------------------------------------------------------------------------------------- |
| scheduled_event_id | The Id of the [WorkflowTaskScheduled](#workflowtaskscheduled) Event that this Workflow Task corresponds to. |
| started_event_id   | The Id of the [WorkflowTaskStarted](#workflowtaskstarted) Event that this Task corresponds to.              |
| identity           | Identity of the [Worker](/workers#worker) that completed this Task.                                         |
| binary_checksum    | Binary Id of the Worker that completed this Task.                                                           |

The SDK client picked up the Workflow Task, processed new history events, and may or may not ask the [Temporal Server](/clusters#temporal-server) to do additional work.
It is possible for the following events to still occur:

- [ActivityTaskScheduled](#activitytaskscheduled)
- [TimerStarted](#timerstarted)
- [UpsertWorkflowSearchAttributes](#upsertworkflowsearchattributes)
- [MarkerRecorded](#markerrecorded)
- [StartChildWorkflowExecutionInitiated](#startchildworkflowexecutioninitiated)
- [RequestCancelExternalWorkflowExecutionInitiated](#requestcancelexternalworkflowexecutioninitiated)
- [SignalExternalWorkflowExecutionInitiated](#signalexternalworkflowexecutioninitiated)
- [WorkflowExecutionCompleted](#workflowexecutioncompleted)
- [WorkflowExecutionFailed](#workflowexecutionfailed)
- [WorkflowExecutionCanceled](#workflowexecutioncanceled)
- [WorkflowExecutionContinuedAsNew](#workflowexecutioncontinuedasnew)

### WorkflowTaskTimedOut

This [Event](/workflows#event) type indicates that the [Workflow Task](/workers#workflow-task) encountered a [timeout](/encyclopedia/detecting-workflow-failures#workflow-task-timeout).
Either an SDK client with a local cache was not available at the time, or it took too long for the SDK client to process the Task.

| Field              | Description                                                                                                 |
| ------------------ | ----------------------------------------------------------------------------------------------------------- |
| scheduled_event_id | The Id of the [WorkflowTaskScheduled](#workflowtaskscheduled) Event that this Workflow Task corresponds to. |
| started_event_id   | The Id of the [WorkflowTaskStarted](#workflowtaskstarted) Event that this Task corresponds to.              |
| timeout_type       | The type of timeout that has occurred.                                                                      |

### WorkflowTaskFailed

This [Event](/workflows#event) type indicates that the [Workflow Task](/workers#workflow-task) encountered a failure.
Usually this means that the Workflow was non-deterministic.
However, the Workflow reset functionality also uses this Event.

| Field              | Description                                                                                                                                  |
| ------------------ | -------------------------------------------------------------------------------------------------------------------------------------------- |
| scheduled_event_id | The Id of the [WorkflowTaskScheduled](#workflowtaskscheduled) Event that this Workflow Task corresponds to.                                  |
| started_event_id   | The Id of the [WorkflowTaskStarted](#workflowtaskstarted) Event that this Workflow Task corresponds to.                                      |
| failure            | Details for the Workflow Task's failure.                                                                                                     |
| identity           | The identity of the [Worker](/workers#worker) that failed this Task. The Worker must be explicitly defined to return a value for this field. |
| base_run_id        | The original [Run Id](/workflows#run-id) of the Workflow.                                                                                    |
| new_run_id         | The Run Id of the reset Workflow.                                                                                                            |
| fork_event_version | Identifies the Event version that was forked off to the reset Workflow.                                                                      |
| binary_checksum    | The Binary Id of the Worker that failed this Task. The Worker must be explicitly defined to return a value for this field.                   |

### ActivityTaskScheduled

This [Event](/workflows#event) type indicates that an [Activity Task](/workers#activity-task) was scheduled.
The SDK client should pick up this Activity Task and execute.
This Event type contains Activity inputs, as well as Activity Timeout configurations.

| Field                            | Description                                                                                                                                                               |
| -------------------------------- | ------------------------------------------------------------------------------------------------------------------------------------------------------------------------- |
| activity_id                      | The identifier assigned to this Activity by a [Worker](/workers#worker) or user.                                                                                          |
| activity_type                    | The [type of Activity](/activities#activity-type) that was scheduled.                                                                                                     |
| namespace                        | Namespace of the Workflow that the [Activity](/activities) resides in.                                                                                                    |
| task_queue                       | The [Task Queue](/workers#task-queue) that this Activity Task was enqueued in.                                                                                            |
| header                           | Information passed by the sender of the [Signal](/encyclopedia/workflow-message-passing#sending-signals) that is copied into the [Workflow Task](/workers#workflow-task). |
| input                            | Information that is deserialized by the SDK to provide arguments to the [Workflow](/workflows) function.                                                                  |
| schedule_to_close_timeout        | The amount of time that a caller will wait for Activity completion. Limits the amount of time that retries will be attempted for this Activity.                           |
| schedule_to_start_timeout        | Limits the time that an Activity Task can stay in a Task Queue. This timeout cannot be retried.                                                                           |
| start_to_close_timeout           | Maximum amount of execution time that an Activity is allowed after being picked up by a Worker. This timeout is retryable.                                                |
| heartbeat_timeout                | Maximum amount of time allowed between successful Worker heartbeats.                                                                                                      |
| workflow_task_completed_event_id | The Id of the [WorkflowTaskCompleted](#workflowtaskcompleted) that the Event was reported with.                                                                           |
| retry_policy                     | The amount of retries as determined by the service's dynamic configuration. Retries will happen until `schedule_to_close_timeout` is reached.                             |

### ActivityTaskStarted

This [Event](/workflows#event) type indicates that an [Activity Task Execution](/workers#activity-task-execution) was started.
The SDK Worker picked up the Activity Task and started processing the [Activity](/activities) invocation.
Note, however, that this Event is not written to History until the terminal Event (like [ActivityTaskCompleted](#activitytaskcompleted) or [ActivityTaskFailed](#activitytaskfailed)) occurs.

| Field              | Description                                                                                                          |
| ------------------ | -------------------------------------------------------------------------------------------------------------------- |
| scheduled_event_id | The Id of the [ActivityTaskScheduled](#activitytaskscheduled) Event that this Task corresponds to.                   |
| identity           | Identifies the [Worker](/workers#worker) that started the Task.                                                      |
| request_id         | Identifies the Activity Task request.                                                                                |
| attempt            | The number of attempts that have been made to complete this Task.                                                    |
| last_failure       | Details from the most recent failure Event. Only assigned values if the Task has previously failed and been retried. |

### ActivityTaskCompleted

This [Event](/workflows#event) type indicates that the [Activity Task](/workers#activity-task) has completed.
The SDK client has picked up and successfully completed the Activity Task.
This Event type contains [Activity Execution](/activities#activity-execution) results.

| Field              | Description                                                                                                    |
| ------------------ | -------------------------------------------------------------------------------------------------------------- |
| result             | Serialized result of a completed [Activity](/activities).                                                      |
| scheduled_event_id | The Id of the [ActivityTaskScheduled](#activitytaskscheduled) Event that this completion Event corresponds to. |
| started_event_id   | The Id of the [ActivityTaskStarted](#activitytaskstarted) Event that this Task corresponds to.                 |
| identity           | Identity of the [Worker](/workers#worker) that completed this Task.                                            |

### ActivityTaskFailed

This [Event](/workflows#event) type indicates that the [Activity Task](/workers#activity-task) has failed.
The SDK client picked up the Activity Task but unsuccessfully completed it.
This Event type contains [Activity Execution](/activities#activity-execution) errors.

| Field              | Description                                                                                                 |
| ------------------ | ----------------------------------------------------------------------------------------------------------- |
| failure            | Serialized result of a [Workflow](/workflows) failure.                                                      |
| scheduled_event_id | The Id of the [ActivityTaskScheduled](#activitytaskscheduled) Event that this failure Event corresponds to. |
| started_event_id   | The Id of the [ActivityTaskStarted](#activitytaskstarted) Event that this failure corresponds to.           |
| retry_state        | The reason provided for whether the Task should or shouldn't be retried.                                    |

### ActivityTaskTimedOut

This [Event](/workflows#event) type indicates that the Activity has timed out according to the [Temporal Server](/clusters#temporal-server), due to one of these [Activity](/activities) timeouts: [Schedule-to-Close Timeout](/encyclopedia/detecting-activity-failures#schedule-to-close-timeout) and [Schedule-to-Start Timeout](/encyclopedia/detecting-activity-failures#schedule-to-start-timeout).

| Field              | Description                                                                                                 |
| ------------------ | ----------------------------------------------------------------------------------------------------------- |
| failure            | Serialized result of a [Workflow](/workflows) failure.                                                      |
| scheduled_event_id | The Id of the [ActivityTaskScheduled](#activitytaskscheduled) Event that this timeout Event corresponds to. |
| started_event_id   | The Id of the [ActivityTaskStarted](#activitytaskstarted) Event that this timeout corresponds to.           |
| retry_state        | The reason provided for whether the Task should or shouldn't be retried.                                    |
| timeout_type       | The type of timeout that led to this Event, e.g., Start-to-Close, Schedule-to-Close, Schedule-to-Start.     |

You can run a Workflow containing an Activity Execution that takes longer than the Start-to-Close Timeout you set and use a RetryPolicy that sets MaxAttempts to 1 so it does not retry indefinitely.
When the Activity times out, you will observe that the `ActivityTaskTimedOut` Event contains other attributes missing from the documentation, including the type of timeout that led to the Event.

### ActivityTaskCancelRequested

This [Event](/workflows#event) type indicates that a request to [cancel](/activities#cancellation) the [Activity](/activities) has occurred.

| Field                            | Description                                                                                                |
| -------------------------------- | ---------------------------------------------------------------------------------------------------------- |
| scheduled_event_id               | The Id of the [ActivityTaskScheduled](#activitytaskscheduled) Event that this cancel Event corresponds to. |
| workflow_task_completed_event_id | The Id of the [WorkflowTaskCompleted](#workflowtaskcompleted) that the Event was reported with.            |

### ActivityTaskCanceled

This [Event](/workflows#event) type indicates that the [Activity](/activities) has been [canceled](/activities#cancellation).

| Field                            | Description                                                                                                                |
| -------------------------------- | -------------------------------------------------------------------------------------------------------------------------- |
| details                          | Additional information reported by the Activity upon confirming cancelation.                                               |
| latest_cancel_requested_event_id | Id of the most recent [ActivityTaskCancelRequested](#activitytaskcancelrequested) Event which refers to the same Activity. |
| scheduled_event_id               | The Id of the [ActivityTaskScheduled](#activitytaskscheduled) Event that this cancelation corresponds to.                  |
| started_event_id                 | The Id of the [ActivityTaskStarted](#activitytaskstarted) Event that this cancelation corresponds to.                      |
| identity                         | Identifies the [Worker](/workers#worker) that requested cancelation.                                                       |

### TimerStarted

This [Event](/workflows#event) type indicates a timer has started.

| Field                            | Description                                                                                     |
| -------------------------------- | ----------------------------------------------------------------------------------------------- |
| timer_id                         | The Id assigned for the timer by a [Worker](/workers#worker) or user.                           |
| start_to_fire_timeout            | Amount of time to elapse before the timer fires.                                                |
| workflow_task_completed_event_id | The Id of the [WorkflowTaskCompleted](#workflowtaskcompleted) that the Event was reported with. |

### TimerFired

This [Event](/workflows#event) type indicates a timer has fired.

| Field            | Description                                                           |
| ---------------- | --------------------------------------------------------------------- |
| timer_id         | The Id assigned for the timer by a [Worker](/workers#worker) or user. |
| started_event_id | The Id of the [TimerStarted](#timerstarted) Event itself.             |

### TimerCanceled

This [Event](/workflows#event) type indicates a Timer has been canceled.

| Field                            | Description                                                                                     |
| -------------------------------- | ----------------------------------------------------------------------------------------------- |
| timer_id                         | The Id assigned for the timer by a [Worker](/workers#worker) or user.                           |
| started_event_id                 | The Id of the [TimerStarted](#timerstarted) Event itself.                                       |
| workflow_task_completed_event_id | The Id of the [WorkflowTaskCompleted](#workflowtaskcompleted) that the Event was reported with. |

### RequestCancelExternalWorkflowExecutionInitiated

This [Event](/workflows#event) type indicates that a [Workflow](/workflows) has requested that the [Temporal Server](/clusters#temporal-server) try to cancel another Workflow.

| Field                            | Description                                                                                     |
| -------------------------------- | ----------------------------------------------------------------------------------------------- |
| workflow_task_completed_event_id | The Id of the [WorkflowTaskCompleted](#workflowtaskcompleted) that the Event was reported with. |
| namespace                        | [Namespace](/namespaces) of the Workflow that`s going to be signaled for execution.             |
| workflow_execution               | Identifies the Workflow and the run of the [Workflow Execution](/workflows#workflow-execution). |
| child_workflow_only              | Set to true if this Workflow is a child of the Workflow which issued the cancelation request.   |
| reason                           | Information provided by the user or client for Workflow cancelation.                            |

### RequestCancelExternalWorkflowExecutionFailed

This [Event](/workflows#event) type indicates that [Temporal Server](/clusters#temporal-server) could not cancel the targeted [Workflow](/workflows).
This is usually because the target Workflow could not be found.

| Field                            | Description                                                                                     |
| -------------------------------- | ----------------------------------------------------------------------------------------------- |
| workflow_task_completed_event_id | The Id of the [WorkflowTaskCompleted](#workflowtaskcompleted) that the Event was reported with. |
| namespace                        | [Namespace](/namespaces) of the Workflow that failed to cancel.                                 |
| workflow_execution               | Identifies the Workflow and the run of the [Workflow Execution](/workflows#workflow-execution). |
| initiated_event_id               | Id of the [RequestCancelExternalWorkflowExecutionInitiated] Event this failure corresponds to.  |

### ExternalWorkflowExecutionCancelRequested

This [Event](/workflows#event) type indicates that the [Temporal Server](/clusters#temporal-server) has successfully requested the cancelation of the target [Workflow](/workflows).

| Field              | Description                                                                                                                                                       |
| ------------------ | ----------------------------------------------------------------------------------------------------------------------------------------------------------------- |
| initiated_event_id | Id of the [RequestCancelExternalWorkflowExecutionInitiated](#requestcancelexternalworkflowexecutioninitiated) Event that this cancelation request corresponds to. |
| namespace          | [Namespace](/namespaces) of the Workflow that was requested to cancel.                                                                                            |
| workflow_execution | Identifies the Workflow and the run of the [Workflow Execution](/workflows#workflow-execution).                                                                   |

### ExternalWorkflowExecutionSignaled

This [Event](/workflows#event) type indicates that the [Temporal Server](/clusters#temporal-server) has successfully [Signaled](/encyclopedia/workflow-message-passing#sending-signals) the targeted [Workflow](/workflows).

| Field              | Description                                                                                                                      |
| ------------------ | -------------------------------------------------------------------------------------------------------------------------------- |
| initiated_event_id | Id of the [SignalExternalWorkflowExecutionInitiated](#signalexternalworkflowexecutioninitiated) Event this Event corresponds to. |
| namespace          | [Namespace](/namespaces) of the Workflow that was signaled to.                                                                   |
| workflow_execution | Identifies the Workflow and the run of the [Workflow Execution](/workflows#workflow-execution).                                  |

### MarkerRecorded

This [Event](/workflows#event) type is transparent to the [Temporal Server](/clusters#temporal-server) .
The Server will only store it and will not try to understand it.
The SDK client may use it for local activities or side effects.

| Field                            | Description                                                                                                                              |
| -------------------------------- | ---------------------------------------------------------------------------------------------------------------------------------------- |
| marker_name                      | Identifies various markers.                                                                                                              |
| details                          | Serialized information recorded in the marker.                                                                                           |
| workflow_task_completed_event_id | The Id of the [WorkflowTaskCompleted](#workflowtaskcompleted) that the Event was reported with.                                          |
| header                           | Information passed by the sender of the [Signal](/encyclopedia/workflow-message-passing#sending-signals) that is copied into the marker. |
| failure                          | Serialized result of a [Workflow](/workflows) failure.                                                                                   |

### StartChildWorkflowExecutionInitiated

This [Event](/workflows#event) type indicates that the [Temporal Server](/clusters#temporal-server) will try to start a Child Workflow.

| Field         | Description                                     |
| ------------- | ----------------------------------------------- |
| namespace     | [Namespace](/namespaces) of the Child Workflow. |
| workflow_id   | Identifies the Child Workflow.                  |
| workflow_type | The name/type of Workflow that was initiated.   |

### StartChildWorkflowExecutionFailed

This [Event](/workflows#event) type indicates a [Child Workflow Execution](/encyclopedia/child-workflows) cannot be started / triggered.
It is usually due to a Child Workflow Id collision.

| Field                            | Description                                                                                                              |
| -------------------------------- | ------------------------------------------------------------------------------------------------------------------------ |
| namespace                        | [Namespace](/namespaces) of the Child Workflow.                                                                          |
| workflow_id                      | Identifies the Child Workflow.                                                                                           |
| workflow_type                    | The name/type of Workflow that has failed.                                                                               |
| initiated_event_id               | Id of the [StartChildWorkflowExecutionInitiated](#startchildworkflowexecutioninitiated) Event this Event corresponds to. |
| workflow_task_completed_event_id | The Id of the [WorkflowTaskCompleted](#workflowtaskcompleted) that the Event was reported with.                          |

### ChildWorkflowExecutionStarted

This [Event](/workflows#event) type indicates a [Child Workflow Execution](/encyclopedia/child-workflows) has successfully started / triggered.
This would also cause the [WorkflowExecutionStarted](#workflowexecutionstarted) to be recorded for the Workflow that has started.

| Field              | Description                                                                                                                                           |
| ------------------ | ----------------------------------------------------------------------------------------------------------------------------------------------------- |
| namespace          | [Namespace](/namespaces) of the Child Workflow.                                                                                                       |
| initiated_event_id | Id of the [StartChildWorkflowExecutionInitiated](#startchildworkflowexecutioninitiated) Event this Event corresponds to.                              |
| workflow_execution | Identifies the Workflow and the run of the Workflow Execution.                                                                                        |
| workflow_type      | The name/type of Workflow that has started execution.                                                                                                 |
| header             | Information passed by the sender of the [Signal](/encyclopedia/workflow-message-passing#sending-signals) that is copied into the Child Workflow Task. |

### ChildWorkflowExecutionCompleted

This [Event](/workflows#event) type indicates that the [Child Workflow Execution](/encyclopedia/child-workflows) has successfully completed.
This would also cause the [WorkflowExecutionCompleted](#workflowexecutioncompleted) to be recorded for the [Workflow](/workflows) that has completed.

| Field              | Description                                                                                                              |
| ------------------ | ------------------------------------------------------------------------------------------------------------------------ |
| result             | Serialized result of the completed Child Workflow.                                                                       |
| namespace          | [Namespace](/namespaces) of the completed Child Workflow.                                                                |
| workflow_execution | Identifies the Workflow and the run of the [Workflow Execution](/workflows#workflow-execution).                          |
| workflow_type      | The name/type of Workflow that was completed.                                                                            |
| initiated_event_id | Id of the [StartChildWorkflowExecutionInitiated](#startchildworkflowexecutioninitiated) Event this Event corresponds to. |
| started_event_id   | Id of the [ChildWorkflowExecutionStarted](#childworkflowexecutionstarted) Event this Event corresponds to.               |

### ChildWorkflowExecutionFailed

This [Event](/workflows#event) type indicates that the [Child Workflow Execution](/encyclopedia/child-workflows) has unsuccessfully completed.
This would also cause the [WorkflowExecutionFailed](#workflowexecutionfailed) to be recorded for the Workflow that has failed.

| Field              | Description                                                                                                              |
| ------------------ | ------------------------------------------------------------------------------------------------------------------------ |
| failure            | Serialized result of a [Workflow](/workflows) failure.                                                                   |
| namespace          | [Namespace](/namespaces) of the Child Workflow that failed.                                                              |
| workflow_execution | Identifies the Workflow and the run of the [Workflow Execution](/workflows#workflow-execution).                          |
| workflow_type      | The name/type of Workflow that has failed.                                                                               |
| initiated_event_id | Id of the [StartChildWorkflowExecutionInitiated](#startchildworkflowexecutioninitiated) Event this Event corresponds to. |
| started_event_id   | Id of the [ChildWorkflowExecutionStarted](#childworkflowexecutionstarted) Event this failure corresponds to.             |
| retry_state        | The reason provided for whether the Task should or shouldn't be retried.                                                 |

### ChildWorkflowExecutionCanceled

This [Event](/workflows#event) type indicates that the Child Workflow Execution has been canceled.
This would also cause the [WorkflowExecutionCanceled](#workflowexecutioncanceled) to be recorded for the Workflow that was canceled.

| Field              | Description                                                                                                              |
| ------------------ | ------------------------------------------------------------------------------------------------------------------------ |
| details            | Additional information reported by the Child Workflow upon cancelation.                                                  |
| namespace          | [Namespace](/namespaces) of the Child Workflow that was canceled.                                                        |
| workflow_execution | Identifies the Workflow and the run of the [Workflow Execution](/workflows#workflow-execution).                          |
| workflow_type      | The name/type of Workflow that was canceled.                                                                             |
| initiated_event_id | Id of the [StartChildWorkflowExecutionInitiated](#startchildworkflowexecutioninitiated) Event this Event corresponds to. |
| started_event_id   | Id of the [ChildWorkflowExecutionStarted](#childworkflowexecutionstarted) Event this cancelation corresponds to.         |

### ChildWorkflowExecutionTimedOut

This Event type indicates that the [Child Workflow Execution](/encyclopedia/child-workflows) has timed out by the [Temporal Server](/clusters#temporal-server).
This would also cause the [WorkflowExecutionTimeOut](#workflowexecutiontimedout) to be recorded for the Workflow that timed out.

| Field              | Description                                                                                                              |
| ------------------ | ------------------------------------------------------------------------------------------------------------------------ |
| namespace          | [Namespace](/namespaces) of the Child Workflow.                                                                          |
| workflow_execution | Identifies the Workflow and the run of the Workflow Execution.                                                           |
| workflow_type      | The name/type of Workflow that has timed out.                                                                            |
| initiated_event_id | Id of the [StartChildWorkflowExecutionInitiated](#startchildworkflowexecutioninitiated) Event this Event corresponds to. |
| started_event_id   | Id of the [ChildWorkflowExecutionStarted](#childworkflowexecutionstarted) Event that this timeout corresponds to.        |
| retry_state        | The reason provided for whether the Task should or shouldn't be retried.                                                 |

### ChildWorkflowExecutionTerminated

This [Event](/workflows#event) type indicates that the Child Workflow Execution has been terminated.
This would also cause the [WorkflowExecutionTerminated](#workflowexecutionterminated) to be recorded for the Workflow that was terminated.

| Field              | Description                                                                                                              |
| ------------------ | ------------------------------------------------------------------------------------------------------------------------ |
| namespace          | [Namespace](/namespaces) of the Child Workflow.                                                                          |
| workflow_execution | Identifies the Workflow and the run of the Workflow Execution.                                                           |
| workflow_type      | The name/type of Workflow that was terminated.                                                                           |
| initiated_event_id | Id of the [StartChildWorkflowExecutionInitiated](#startchildworkflowexecutioninitiated) Event this Event corresponds to. |
| started_event_id   | Id of the [ChildWorkflowExecutionStarted](#childworkflowexecutionstarted) Event that this termination corresponds to.    |
| retry_state        | The reason provided for whether the Task should or shouldn't be retried.                                                 |

### SignalExternalWorkflowExecutionInitiated

This [Event](/workflows#event) type indicates that the [Temporal Server](/clusters#temporal-server) will try to [Signal](/encyclopedia/workflow-message-passing#sending-signals) the targeted [Workflow](/workflows).
This Event type contains the Signal name, as well as a Signal payload.

| Field                            | Description                                                                                     |
| -------------------------------- | ----------------------------------------------------------------------------------------------- |
| workflow_task_completed_event_id | The Id of the [WorkflowTaskCompleted](#workflowtaskcompleted) that the Event was reported with. |
| namespace                        | [Namespace](/namespaces) of the Workflow that's to be signaled.                                 |
| workflow_execution               | Identifies the Workflow and the run of the [Workflow Execution](/workflows#workflow-execution). |
| signal_name                      | The name/type of Signal to be fired.                                                            |
| input                            | Information that is deserialized by the SDK to provide arguments to the Workflow Function.      |
| child_workflow_only              | Set to true if this Workflow is a child of the Workflow which issued the cancelation request.   |
| header                           | Information to be passed from the Signal to the targeted Workflow.                              |

### SignalExternalWorkflowExecutionFailed

This [Event](/workflows#event) type indicates that the [Temporal Server](/clusters#temporal-server) cannot Signal the targeted [Workflow](/workflows), usually because the Workflow could not be found.

| Field                            | Description                                                                                                                                                                                                       |
| -------------------------------- | ----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- |
| workflow_task_completed_event_id | The Id of the [WorkflowTaskCompleted](#workflowtaskcompleted) that the Event was reported with.                                                                                                                   |
| namespace                        | [Namespace](/namespaces) of the Workflow that failed to execute.                                                                                                                                                  |
| workflow_execution               | Identifies the Workflow and the run of the [Workflow Execution](/workflows#workflow-execution).                                                                                                                   |
| initiated_event_id               | Id of the [RequestCancelExternalWorkflowExecutionInitiated](#requestcancelexternalworkflowexecutioninitiated) Event this failure [signal](/encyclopedia/workflow-message-passing#sending-signals) corresponds to. |

### UpsertWorkflowSearchAttributes

This [Event](/workflows#event) type indicates that the Workflow [Search Attributes](/visibility#search-attribute) should be updated and synchronized with the visibility store.

| Field                            | Description                                                                                  |
| -------------------------------- | -------------------------------------------------------------------------------------------- |
| workflow_task_completed_event_id | The [WorkflowTaskCompleted](#workflowtaskcompleted) Event reported the Event with this Id.   |
| search_attributes                | Provides data for setting up a Workflow's [Search Attributes](/visibility#search-attribute). |

### WorkflowExecutionUpdateAcceptedEvent

This [Event](/workflows#event) type indicates that a [Workflow Execution](/workflows#workflow-execution) has accepted an [Update](/encyclopedia/workflow-message-passing#sending-updates) for execution.
The original request input payload is both indicated and stored by this Event, as it generates no Event when initially requesting an Update.

| Field                                | Description                                                                                                                                                            |
| ------------------------------------ | ---------------------------------------------------------------------------------------------------------------------------------------------------------------------- |
| protocol_instance_id                 | The instance of the Update protocol with this Id is executing this Update.                                                                                             |
| accepted_request_message_id          | The Id of the request message sent by [Temporal Server](/clusters#temporal-server) to the [Worker](/workers#worker).                                                   |
| accepted_request_sequencing_event_id | Execute this Update after the Event with this Id.                                                                                                                      |
| accepted_request                     | The request input and metadata initially provided by the invoker of the Update and subsequently relayed by Temporal Server to the Worker for acceptance and execution. |

### WorkflowExecutionUpdateCompletedEvent

This [Event](/workflows#event) type indicates that a [Workflow Execution](/workflows#workflow-execution) has executed an [Update](/encyclopedia/workflow-message-passing#sending-updates) to completion.

| Field             | Description                                                                                                                                  |
| ----------------- | -------------------------------------------------------------------------------------------------------------------------------------------- |
| meta              | The metadata associated with this Update, sourced from the initial request.                                                                  |
| accepted_event_id | The Id of the [WorkflowExecutionUpdateAcceptedEvent](#workflowexecutionupdateacceptedevent) The Platform accepted this Update for execution. |
| outcome           | The outcome of execution of this Update whether the execution resulted in a success or a failure.                                            |

### NexusOperationScheduled

This Event type indicates that a Nexus Operation scheduled by a caller Workflow.
The caller's [Nexus Machinery](/glossary#nexus-machinery) will attempt to start the Nexus Operation.
This Event type contains Nexus Operation input and the Operation request ID.

| Field                            | Description                                                                                                                                                                                                                                                                                               |
| :------------------------------- | :-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- |
| endpoint                         | Endpoint name, must exist in the endpoint registry.                                                                                                                                                                                                                                                       |
| service                          | Service name.                                                                                                                                                                                                                                                                                             |
| operation                        | Operation name.                                                                                                                                                                                                                                                                                           |
| input                            | Input for the operation. The server converts this into Nexus request content and the appropriate content headers internally when sending the StartOperation request. On the handler side, if it is also backed by Temporal, the content is transformed back to the original Payload stored in this event. |
| schedule_to_close_timeout        | Schedule-to-close timeout for this operation. Indicates how long the caller is willing to wait for operation completion. Calls are retried internally by the server.                                                                                                                                      |
| nexus_header                     | Header to attach to the Nexus request. Note these headers are not the same as Temporal headers on internal activities and child Workflows, these are transmitted to Nexus operations that may be external and are not traditional payloads.                                                               |
| workflow_task_completed_event_id | The ID of the [WorkflowTaskCompleted](#workflowtaskcompleted) event that the corresponding ScheduleNexusOperation command was reported with.                                                                                                                                                              |
| request_id                       | A unique ID generated by the History Service upon creation of this event. The ID will be transmitted with all Nexus StartOperation requests and is used as an idempotency key.                                                                                                                            |
| endpoint_id                      | Endpoint ID as resolved in the endpoint registry at the time this event was generated. This is stored on the event and used internally by the server in case the endpoint is renamed from the time the event was originally scheduled.                                                                    |

### NexusOperationStarted

This Event type indicates that a Nexus Operation Execution was started.
This Event is added to the caller's Workflow History for Asynchronous Nexus Operations, for example those that are backed by a Workflow.
The Event is not added to the caller's Workflow History for Synchronous Nexus Operations, since they transition directly to [NexusOperationCompleted](#nexusoperationcompleted) or another final state such as [NexusOperationFailed](#nexusoperationfailed) when the response is provided synchronously by the Nexus handler.

| Field              | Description                                                                                                                                 |
| :----------------- | :------------------------------------------------------------------------------------------------------------------------------------------ |
| scheduled_event_id | The ID of the [NexusOperationScheduled](#nexusoperationscheduled) event this task corresponds to.                                           |
| operation_id       | The operation ID returned by the Nexus handler in the response to the StartOperation request. This ID is used when canceling the operation. |
| request_id         | The request ID allocated at schedule time.                                                                                                  |

### NexusOperationCompleted

This Event type indicates that a Nexus Operation has completed successfully.
The caller's Workflow History records the result of a successful Nexus Operation with this event for synchronous and asynchronous Nexus Operations.
This Event type contains Nexus Operation results.

| Field              | Description                                                                                                                                                          |
| :----------------- | :------------------------------------------------------------------------------------------------------------------------------------------------------------------- |
| scheduled_event_id | The ID of the [NexusOperationScheduled](#nexusoperationscheduled) event. Uniquely identifies this operation.                                                         |
| result             | Serialized result of the Nexus operation. The response of the Nexus handler. Delivered either via a completion callback or as a response to a synchronous operation. |
| request_id         | The request ID allocated at schedule time.                                                                                                                           |

### NexusOperationFailed

This Event type indicates that a Nexus Operation has failed.
The caller's Workflow History records a failed Nexus Operation with this event both for synchronous and asynchronous Nexus Operations.
For example, when a Nexus Handler responds synchronously with a non-retryable error or when a Workflow that backs an Operation fails, resulting in a [WorkflowExecutionFailed](#workflowexecutionfailed) Event.
When an SDK client picks up a Nexus Operation, the Nexus handler asynchronously starts an underlying Workflow, which subsequently results in [WorkflowExecutionFailed](#workflowexecutionfailed).
This Event type contains a Nexus Operation failure.

| Field              | Description                                                                                                   |
| :----------------- | :------------------------------------------------------------------------------------------------------------ |
| scheduled_event_id | The ID of the [NexusOperationScheduled](#nexusoperationscheduled)` event. Uniquely identifies this operation. |
| failure            | Failure details. A NexusOperationFailureInfo wrapping an ApplicationFailureInfo.                              |
| request_id         | The request ID allocated at schedule time.                                                                    |

### NexusOperationTimedOut

This Event type indicates that a Nexus Operation has timed out according to the Temporal Server, due to one of these Nexus Operation timeouts: Schedule-to-Close Timeout.
| Field | Description |
| :---- | :---- |
| scheduled_event_id | The ID of the [NexusOperationScheduled](#nexusoperationscheduled)` event. Uniquely identifies this operation. |
| failure | Failure details. A NexusOperationFailureInfo wrapping a CanceledFailureInfo. |
| request_id | The request ID allocated at schedule time. |

### NexusOperationCancelRequested

This Event type indicates that the Workflow that scheduled a Nexus Operation requested to cancel it.
| Field | Description |
| :---- | :---- |
| scheduled_event_id | The id of the [NexusOperationScheduled](#nexusoperationscheduled)` event this cancel request corresponds to. |
| workflow_task_completed_event_id | The [WorkflowTaskCompleted](#workflowtaskcompleted) event that the corresponding RequestCancelNexusOperation command was reported with. |

### NexusOperationCanceled

This Event type indicates that a Nexus Operation has resolved as canceled.
| Field | Description |
| :---- | :---- |
| scheduled_event_id | The ID of the [NexusOperationScheduled](#nexusoperationscheduled)` event. Uniquely identifies this operation. |
| failure | Cancellation details. |
| request_id | The request ID allocated at schedule time. |
